The present invention relates to photocontrolled ion-flow electron radiography apparatus for x-ray imaging and, more particularly, to novel ion-flow electron radiographic apparatus having a multi-layered mesh structure of reduced mechanical complexity
Xeroradiographic imaging techniques, wherein x-radiation differentially absorbed in an object causes the deposition of an electrostatic image on an insulative sheet, for subsequent development by xerographic techniques, is known for replacement of conventional x-ray imaging techniques using the screen-film system. Pending U.S. patent application Ser. No. 716,088, filed Aug. 20, 1976 and assigned to the assignee of the present invention, discloses and claims methods and apparatus for x-ray imaging by photocontrolled ion flow electron radiography. The apparatus in the afore-mentioned pending patent application, incorporated herein by reference, comprises an electron structure of a conductive sheet receiving the differentially-absorbed x-radiation and supporting a plastic sheet forming one boundary of an air gap. A second electrode comprises a conductive mesh supporting, of a surface thereof facing the plastic sheet, a layer of photoconductive material which is precharged prior to x-ray exposure. A phosphor plaque is moved into abutment with the pre-charged photoconductive layer during x-ray exposure and acts to convert x-ray quanta to photons of visible light for rendering underlying portions of the photoconductive layer to the conductive condition and removing charge therefrom to the conductive screen. After exposure, a source provides a stream of ions of the same polarity as that utilized for precharging the photoconductive layer, for movement through the photoconductive mesh toward the plastic sheet. The ion flow is modulated by the electric charge pattern stored at the photoconductive layer to deposit a charge pattern on the plastic sheet, for subsequent development by xerographic techniques. As the phosphor plaque must be moved into engagement with the photoconductive layer during x-ray exposure, and must be removed from the gap to allow the controlled ion flow to reach the plastic sheet, considerable mechanical complexity results. It is desirable to gain the advantage of photocontrolled ion-flow electron radiography (i.e. high device gain, with reduced x-ray dosage to a patient) while reducing the mechanical complexity of the recording device.